The present invention relates to a method of repairing damage to an oxidation-resistant coating on a carbon-carbon composite. The invention is based, in part, on utilization of polymeric ceramic precursors disclosed in the parent application identified above, whose entire specification and claims are specifically incorporated herein by reference.
As is well known, carbon-carbon composites are formed of carbon fibers, typically woven into two-dimensional weaves which are stacked and surrounded by a dense carbon matrix. Such composites can be flat or shaped into three-dimensional structures and are widely utilized in the aerospace industry performing many vital components, such as in the Space Shuttle Orbiter Vehicle.
In order to prevent oxidation of the carbon in such carbon-carbon composites, it is common and necessary to apply a layer of an oxidation-resistant ceramic coating onto the surface of the composites. At present ceramic coatings composed primarily of silicon carbide or silicon nitride are used to protect carbon-carbon composites from oxidation. These coatings are applied by known and conventional techniques such as pack cementation, chemical vapor deposition, or a combination of these procedures. Although these methods produce coatings which impart a useful lifetime to the carbon structures, they require extreme conditions and specialized equipment for application. Structures with damage to the oxidation protection coating that result in exposure of the carbon-carbon substrate must be removed from the vehicle and shipped offsite for repair. Techniques which permit repair coatings in the field are or on the shop floor are not available and the result is costly in terms of time and manufacturing procedures, to repair damaged carbon-carbon structures and in the time required to make the repair.